Improvement in manufacture of red colors from copperas



UNITED STATES PATENT OFFICE.

WETHERILL PETERSON, OF PHILADELPHIA, PENNSYLVANIA.

IMPROVEMENT IN MANUFACTURE OF RED COLORS FROM COPPERAS.

Specification forming part of Letters Patent No. 203,936, dated May 21,1878; application filed April 18, 1878.

A To all whom it may concern:

Be it known that I, WETHERILL PETER- SON, of Philadelphia, Pennsylvania,have in vented a Process of Making Venetian Red, Indian Red, and othercolors usually obtained from the oxide of iron by different degrees ofheat, of which process the following is a specification:

My process does not apply to the manufacture of pure oxide of iron, .butto the making of Venetian red, and the other colors above referred tofor pigments where the sulphate of lime is used,'in whole or in part, asa body.

Hitherto these colors have been made in various ways, but chiefly bycalcining the oxide of iron, previously obtained by precipitation orother processes, with sulphate of lime, or by calcining sulphate of iron(copperas) with the sulphate of lime and driving off the acid of thecopperas by heat.

I takesulphate of iron, (copperas,) in powder or crystals, (the refusecopperas obtained from the boiling-pans in the manufacture of copperasand the crystals of copperas not sufficiently large and clean to be soldas cop'- perasmay be used,) and mix the same with lime, eitherquicklime, carbonate of lime, or hydrate of lime (preferably the last)in proper proportions to decompose the sulphate of iron and form oxideof iron and sulphate of lime, adding sufficient sulphate of lime(gypsum) to give the body required, and calcine the whole together inany furnace or vessel, with access of air, until the desired shade ofcolor is obtained, after which the mass is finely ground, so as to formthe Venetian red, Indian red, &c., of commerce.

I have found that one hundred and thirtysix pounds of the hydrate oflime, one hundred and seventy-five pounds of copperas, and

4 four hundred pounds of gypsum, when calcined together, give goodresults. If quicklime is used, about one hundred and four poundsthereof, and if carbonate of lime, about two hundred and twenty poundsthereof, must be used with the last above-named quantity of copperas.

The quantities of lime here stated are a little in excess of thetheoretical quantities required; but the excess is added to insure thethorough neutralization of the acid, which is hurtful in the paint,whereas a slight excess of lime is harmless.

As the gypsum is neutral, and does not affect the reaction, (it beingemployed simply to give body and not color to the product,) it may bealtogether omitted, or a smaller or larger quantity thereof may beemployed, according as a stronger or weaker paint may be required. Forthe same reason, it is also immaterial whether the gypsum is addedbefore or after the calcination.

The advantage of my process consists in avoiding the precipitation ofthe oxide of iron in the liquid way previous to calcination, also inavoiding the loss incident to driving oil the sulphuric acid by heat inthe ordinary processes of calcining sulphate of iron with V gypsum. Bymy process the sulphuric acid is fixed by the lime as sulphate of limeand the process of manufacture much shortened and. cheapened.

I claim- In making Venetian red, Indian red, and the other colorsobtainable from oxide of iron, the process which consists in mixingsulphate of iron with hydrate of lime and calcining the mixture,substantially as set forth.

WETHERILL PETERSON.

Witnesses JOHN I. GREEN, Tnos. A. BURTT.

